Gas bags for a vehicle occupant restraining system are known, which have discharge openings through which, with the gas bag in the deployed state, a part of the gas employed for deployment of the gas bag may be discharged.
By control of the discharge of gas from a deployed gas bag it is possible to obtain an optimum restraining action by the deployed gas bag in a manner adapted to the severity of the accident in an individual case and to the weight of the vehicle occupant. Discharging gas from the gas bag may be allowed for essentially in two different ways: on the one hand discharge openings may be provided in the wall of the gas bag, which are either opened at the outset or are opened by the pressure in the interior of gas bag, and on the other hand by having gas permeable regions in the fabric. A disadvantage in the case of discharge openings formed in the wall is the complexity of manufacture. Furthermore it is not possible to prevent certain fluctuations in the opening pressure in the case of discharge openings adapted to open when a certain pressure is reached.